APES 2.4-2.7

2.4: ECOLOGICAL TOLERANCE

The 3 zones of ecological range of tolerance:

  • Optimal range: Organisms survive, grow, and reproduce

  • Zone of physiological stress: range where organisms survive, but experience some stress such as infertility, lack of growth, decreased activity, etc.

  • Zone of intolerance: the organism will die

2.5: NATURAL DISRUPTIONS TO ECOSYSTEMS

The 3 time frames natural disturbances occur on:

  • Periodic: occurs with regular frequency and intervals

  • Episodic: occasional events with irregular frequency. They can happen at specified intervals but the exact time is unexpected

  • Random: no regular frequency, completely unexpected. Examples include asteroids and earthquakes.

2.6: ADAPTATIONS

Natural selection: Organisms that are better adapted to their environment survive and reproduce more offspring

Individuals without adaptations die off, which leads to evolution

Selective pressure/force: the environmental condition that kills individuals that do not have the adaptation

The environment an organism lives in Determines which traits are adaptations

As environments change, different traits may become adaptations and old traits may become disadvantages

The more rapidly an environment changes, the less likely a species in the environment will be able to adapt to those changes, causing them to migrate or die

The longer the lifespan of the organism, the slower the rate of evolution

2.7: ECOLOGICAL SUCCESSION

Primary Succession: Starts from bare rock in an area with no previous soil formation

  • Moss and Lichen spores carried by the wind grow directly on rocks, breaking them down to form soil

Secondary succession: starts from already established soil in an area where a disturbance cleared out the majority of plant life

Pioneer or early Succession species: They appear first in the stages of succession when the ground is simply bare rock or bare soil after a disturbance

  • Seeds spread by wind or animals

  • Fast growing

  • Tolerant of shallow soil

  • Full sunlight

Mid-succesional species: they appear after Pioneer species have helped develop deeper soil with more nutrients by their cycles of growth/death

  • Fast growing

  • Bigger plants that need deeper soils with more nutrients

  • Sun tolerant

Late successional or climax community species: they appear last in the stages of succession after soil is deepened and enriched with nutrients by cycles of growth and death by early and mid-successional species

  • Slow growing trees

  • Tolerant of shade

  • Requires deer soil for large root networks